Adjustable collimator for radiation therapy



Nov. 8', 1960 2,959,680

D. T. GREEN ADJUSTABLE COLLIMAIOR FOR RADIATION THERAPY Filed March 28,1956 7 Sheets-Sheet 2 Nov. 8, 1960 D. T. GREEN 2,959,630

ADJUSTABLE COLLIIVATOR FOR RADIATION THERAPY Filed March 28, 1956 7Sheets-Sheet 3 ITTGRNE/J Nov. 8, 1960 I ,1', GREEN 2,959,680 IADJUSTABLE COLLiMATOR FOR RADIATION THERAPY Filed March 28, 1956 '7Sheets-Sheet 4 I 1-" INVENTOR.

banana 7, 604'! arm/num- Nov. 8, 1960 D. T. GREEN 2,959,680

ADJUSTABLE COLLIMATOR FOR RADIATION THERAPY 7 Filed March 28, 1956 7Sheets-Sheet 5 INVENTOR. Dow/71.0 7? 6/95! Nov. 8, 1960 D. 1'. GREEN2,959,680

ADJUSTABLE COLLIMATOR FOR RADIATION THERAPY Filed March 28, 1956 7Sheets-Sheet 6 INVENTOR.

Domino 2' 6-0:!

Now.v 8, 1960 D. 'r. GREEN ADJUSTABLE COLLIMATOR FOR RADIATION THERAPY 7Sheets-Sheet 7 Filed March 28, 1956 m T m m Dom no 7 6IN drawn/vi);

United States Patent C) ADJUSTABLE COLLHVIATORFOR RADIATION.

THERAPY r Donald T. Green, Cleveland, Ohio, assignor to Picker X-RayCorporation, Waite; Manufacturing Division, Inc., Cleveland, Ohio, 21corporation'offlhio Filed Mar. 2a, 1956, s Nb. 574,523 20 Claims. or.250-105 This invention relates to improvements in an adjustablecollimator for high'energy rays emanating from a source adapted forradiationitherapy.

An object of the present invention is to. provide means for controllinghigh energy rays of the type described by the use of a plurality of rayabsorbing diaphragms, movably mounted and arranged progressively fromthe source outwardly, and mechanisms for holding the inner sides of animaginary cone or polygonal pyramid whose.

longitudinal axis isthrough the source of high energy rays in alladjusted positions of the diaphragms, and more especially where the apexof said cone or pyramid is located approximately at said source.

A further object of the present invention is to provide another-than-point source of high energy rays and to provide mechanismsfor holding a series of movable diaphragms invarious adjusted positions,and in each of these positions the inner edges of these diaphragms aresubstantially aligned along the slanting sides of an imaginary cone orpyramid, the sides of which extend approximately through the lateraledges of the source,

A further object of the present invention is to provide. a plurality ofray absorbing diaphragms contained Within an expandable housing with thechange in shape of the housing capable of moving one or more of the diaparticularly, with an expandable frame for supporting said sets.

A further object of the present invention is to provide an adjustablecollimator for high energy .rays. having ray absorbing diaphragmsadapted to be'moved tochange the shape of the beam emanating from the,collimator, and having an indicator responsive to the positions of saiddiaphragms and actuated independent of the means for moving saiddiaphragms, whereby backlash'error is eliminated.

A further object of the present inventionis to provide a light sourcehaving a light beam coincidingwitha beam of high energy rays and toprovide crossed cables in the center offsaid beams for. locating bysaidlight beam the center of said ray beam duringuse.

A further object of the present invention is to provide an adjustablecollimator for highenerg'y rays characterized by its structuralsimplicity,-compactncss of assem- Patented N ov. 8, 1 960 2. bly,efiicient ray. absorption of stray rays, ease ofopera: tion, wide rangeof beam shapes, sharp definition of the edges of the beam, minimum sizehousing for a given beam size, and smoothly fashioned housing contoureven though the changing shape of the housing causes the changes inbeamfshape.

Other features of this invention reside in the arrange ment and designof the parts for carrying out their appropriate functions.

Other objects and. advantages of this invention will be apparent fromthe accompanying drawings and description and the essential featureswill be set forth inthe appended claims.

In the drawings,

Fig. 1 is a side elevational view of the adjustable collimator of thepresent invention;

Fig. 2 is a bottom view taken along the line 2-2 of Fig. 1;

Fig. 3 is a vertical longitudinal sectional view taken along the line 33of Fig. 2;

Fig. 3a is an enlarged top plan View of a modified form of diaphragm;

Fig. 3b is a vertical sectional view taken alongthe line 3b-3b of Fig.3a;

Fig. 4 is a horizontal sectional view taken along the line 4 4 of Fig. 3inside the bottom cover, below the expandable frame for supporting thediaphragms, and below the crossed cables;

Fig. 5 is a horizontal sectional view taken along the line 55 of Fig. 3looking upwardly at the bottom most diaphragms, of the pile supported bythe adjustable frame;

Fig. dis a horizontal sectional view taken along the line 66 of Fig. 3;

Fig." 7 is a bottom view similar to Fig. 4 but with. the

diaphragms in the expandedposition shown in Fig. 8;.

Fig; 8 is a vertical :sectionjal view taken along 'theline S8 of "Fig. 7across corners of the collimator;

Fig. 9 is a horizontal sectional view taken along the line 99 of Fig.8;

Fig. 9a is a horizontal sectional view, similar to Fig. 9,

. of a modified form of corner. member and spring attachment;

Fig. 10 is a vertical sectional view taken generally along the lineIll-10 ofFig. S'Wi'th parts omittedl for clarity and other partspartially cutaway; I

Fig. 11 is a vertical sectional view taken generally along the line 11-'-11 of Fig. 3'with portions thereof partially cut away and with partsomitted'for clarity;

Fig. 12 is a sectionalview taken along the line 12--12 of Fig. 11; whileFigs. 13 and 14 are pictorial representations of the shape andsizeranges of. high energy'raybeams that may be achieved by adjustment" ofthe collimator of the presently disclosed embodiment of my inventionwith Figs. 13 and 14 respectively disclosing the size ranges of beams ofsquare and rectangular transverse cross sections.

Before theapparatus here illustrated is specifically described; it isto'be understood that the invention here involved is not limited to thestructural details or arrangement of parts he're'shown sincej adjustablecollimators embodying the present inventionlmaytakevarious rays where adiirect'ed beamof the rays'is required. The present inventionis directedto this problem. Wherever in the specification and" claims the termhighienergy rays is used, or theequivalennit is' intended to includeX-rays in the two to"three million volt region'rays from Cobalt, gammarays or rays of a similar character or more penetrating than that. Thepresent invention is described in connection with a Cobalt source.

The invention will be described with respect to the use of the rays froma therapeutic point of view for treating human beings, although it willbe understood that the invention is useful for controlling high energyrays for any use whatever.

The mounting and control of the source forms no part of the presentinvention except insofar as it provides a fixed primary aperture incombination with the adjustable secondary aperture or opening in thecollimator of the present invention. Any suitable mounting and controlmay be provided, such as disclosed in the copending US. patentapplication filed by Harold E. Johns and John A. MacKay on May 18, 1954,Serial No. 430,- 584, now US. Patent No. 2,844,736, entitled Collimatorfor High Energy X-Ray Beam.

The high energy ray source in the present disclosure is a plurality ofcobalt discs 20. The diameter of these discs is a matter of compromise.It is a question of balancing the disadvantages of a large source withthe economic advantages in a large source of low specific activity. Asource between one and three centimeters in diameter seems to be asuitable compromise with these two considerations in mind. This is thebasis for the use of the phrase other-than-point source hereinaftermentioned.

Although the adjustable collimator is disclosed as forming the rays intoa beam of square or rectangular transverse cross section, they may beformed into a beam having any desired shape in transverse cross sectionwith a closed perimeter. The shape obtained would depend upon the shapeof the beam defining surfaces, the number of diaphragms, and thearrangement of the diaphragms in the collimator.

The description hereinafter will be directed toward describing in detailthe adjustable collimator for forming into a beam high energy raysemanating from the source 20 with this beam taking any desired shape orsize, depending upon the characteristics of the collamator.

A mounting is provided for the collimator to connect it to the sourceand to permit rotation of the collimator about a vertical central axisin Fig. 3 extending longitudinally of the ray beam. Here, source 20 isin a shield 21 consisting of a mass of encasing lead, tungsten alloy orother heavy metal surrounded by a steel case 22. A bearing ring 24 issecured to case 22 by a plurality of circumferentially spaced screws 25.A main collimator bearing ring 26 has an auxiliary ring 27 securedthereto by screws 28 to form the inner half of the cylindrical racewayfor ball bearings 29. Naturally, rings 24, 26 and 27 are all generallyannular in shape so that collimator main ring 26 may be rotated aboutits central axis and concentric with respect to the source 20.Collimator main ring 26 is secured to a collimator base sleeve 31 inFigs. 3 and 6 by a plurality of circumferentially spaced screws 33.Collinator base 32, secured in any suitable manner within the bore ofthe base sleeve 31, such as by bolts (not shown), is formed of an upperbase portion 32a, preferably formed of dense material such as tungstenalloy to provide a fixed aperture and to control leakage radiationoutside the collimator, secured to a lower base portion 32b by screws32c and having a central conical bore 32d to permit downward passage ofthe rays from the source 20.

The collimator includes the collimator base 32 and the structuredescribed hereinafter in detail. It has a plurality of spaced diaphragmsets, here shown as 6 /2 sets but of any satisfactory number, arrangedin pile formation in 13 layers along, and at right angles to, the axisof the beam. The extra half set is provided to give the desireddimensions and operating characteristics in the specifically illustratedconstruction.

Each set is composed of a plurality (here shown as four) of L-shaped,ray absorbing movable diaphragms 35, 36, 37 and 38 in Figs. 3, 5, 7 and8. Diaphragms 35 and 36 are located in one plane or zone extendingtransverse to the beam axis while diaphragms 37 and 38 are located in anadjacent plane or zone. In each plane, the L-shaped diaphragms arenested together to form a pair, so that when they are assembled in themanner shown in Fig. 5, they fit together to leave a square opening inthe center thereof.

Since each diaphragm is substantially identical, only diaphragm 35 inFig. 5 will be described in detail. This diaphragm has two legs 35a and35b joined at a vertex with leg 35a being shorter so as to form thehorizontal leg of the L-shape, as viewed in Fig. 5. These legsrespectively have inner, beam-defining edges 35c and 35d for forming therays emanating from the source 20 into a ray beam. Diaphragm 35 at theupper left in Fig. 3 is formed of joined layers consisting of an innerlead plate 35c having stainless steel facing plates 35f on top andbottom surfaces thereof. Also, at the vertex, a vertically extendingthrough sleeve 35g (Figs. 5 and 8) is located, preferably being of brassmaterial.

A modified form of diaphragm is shown in Figs. 3a and 3b at 135, whichmay be substituted for the dia phragms in the bottom four layers in Fig.3. It has tungsten alloy inserts 135p, 135g mounted by screws andforming beam defining edges 1350, 135d. Tungsten, be ing dense, sharpensthe penumbra of the beam. Facing plates 135 may have bearing portions135f bent over the outer edge of the inner lead plate to serve as ahearing surface for relative movement with the inside surface of thesurrounding housing. Similar bearing portions may be formed by bentextensions of plates 35 in Fig. 3, if so desired.

In each set, the four diaphragms 35 to 38 are arranged so that they areprogressively displaced degrees about the axis of the beam; notediaphragms 35, 37, 36 and 38 in Fig. 5. However, this so-calledprogressive displacement need not be in immediately following orclocltwise order, as illustrated. It should be readily apparent that thenumber of diaphragms in each set, the shape of the opening 40 defined bythe inner edges thereof, and the shape of the diaphragms (other thanL-shape) may be a matter of choice; and that diaphragms may be arrangedto define an opening with any type closed perimeter capable of forming,by the inner edges thereof, the source rays into a ray beam.

Since there are four diaphragms in each set, there are four diaphragmgroups with each group having correspondingly positioned diaphragms,such as one group with all the diaphragms 35, a second group with all ofthe diaphragms 36, etc.

The collimator is provided with interconnected operating mechanisms formoving the diaphragms between the positions shown in Figs. 3 and 8. Inthe illustrated form, there are four operating mechanisms,interconnected by base 32, with each mechanism operatively connectedwith correspondingly positioned diaphragms in each set forming one ofthe four diaphragm groups. Each mechanism adjusts all of thecorrespondingly positioned diaphragms in its group simultaneously, andadjustment of all four op erating mechanisms will move or adjust all ofthe diaphragms.

Collimator base 32 has a housing supported thereby and hanging therefromfor enclosing and supporting the diaphragms 35, 36, 37 and 38. Thishousing has four sides generally forming a square prism in Fig. 3 andexpandable into generally a square pyramid in Fig. 8 while maintainingan unbroken enclosure on its periphery for the diaphragms. Thediaphragms are constrained to move with the walls of the housing so thatthe shape of the housing will determine the shape of the beam opening40. See Figs. 3, 8, 13 and 14.

In the present disclosure, the housing includes in Fig. 5 a plurality ofhousing side wall members 41, 42, 43

ndMapivotally connectedra't 41a, 42a, q-.and\44a. in,

Figs; 1; 3 and ;5 to, base ;32: to, permit relative pivotal movement.'[;]1e ;hinge center ,lines of these pivots in the present constructiondefine asquare, but may within the scope, of ,this inventiondefine anyother rectangle, Whose, sides are paralleljo the sides of the ray beamforming'opening 40 of the diaphragms with the square lying in a planeperpendicular to the beam axis, centered onthetbeam axis, and located asnear the source 20 as practicable so that the inner edges of thediaphragms will linev up well withthe edges ofsource 20. Since each sidewall member has basically the same construction, onlyjside wal1 =member43 wil1'be described in detail. Side wall member '43 has an arm- 43b inFig. 3 having pivot pin 43a at:its upper end and secured at its lowerend to a side wallformed by an outer plate 43c and an. inner plate 43dsecured together and maintained in spaced relationship by a plurality ofspacers 432 and screws :43f.

A plurality o fcorner members (here shown as four in number) 51, 52., 53and;54' operatively connect adjacent side wall members to complete theformation of the housing in Fig. around the diaphragm sets. Each cornermember'isan angle member with theplanar walls thereof. operativelyconnected tornovere'spectively in the planes of the. adjacent"side wallmembers. Since each corner member is identical, only the corner memberwillbedescribecl in detail. It includes two angularly. disposed plates51a and'5l b;conn ected together by. a corner forming connectingportion51c. nection between'cornerimember 51 and the adjacent side wall members41 aim-1,142 is provided by having plate 51a telescoped intgjthefspacebetween platesA-l'c and 41d (1 having plate '51b 'telescoped into thespace between p ates 42 c and 42 1 The contacting side wallsrof theseplates are maehined. fiat so that the cornermembers and side wall jmembers may move telescopically relative to each other between theFdg. 3and 8 positions in the manner ,showninfFig. 11 by the. dotted andfullline positions. i

Although four side, wall members and four corner members areillustrated, it should be readily understood,

that any desired number may be assembled together to form a housingdepending upon the mode of operation.

of the collimator desired and the shape of the ray beam forming opening40.

Means are providedfor operatively connecting a group. of correspondinglypositioned diaphragms to the vertex of each corner member so that thediaphragms are constrained to follow the movement of the housing duringexpansion and contraction thereof. This is shown in Fig. 5 by having alldiaphragms 35 connected to corner member 51 diaphragms 38 to cornermember 52, diaphragms 36 to corner member 53, and diaphragms 37 tocorner member 54. At each corner, a connecting construction is providedincluding control bars 61, 62, 63 and 64. Since each [is identical, onlycontrol bar' 61 'in Fig. 8 will be described. Control bar 61 includestie bar 'or cylindrical rod'61a having stop pin 61b adjacent at' leastits lower end and a plurality of spherical beads 61c and spacers 61dalternately arranged 'in telescopic relation over tie bar 61a with pin61b preventing telescopic disassembly. Each of the beads 610, preferablyformed of brass or other bearing material, has a generally sphericalperipheral surface to form the inner member of a universal jointconnection. Every other one of these beads 610 is located in one of thediaphragm sleeves 35g,

while the remainder are locatedin spacer and spring The operative conp rm 35 q io le l i ov me 0 the ne memw,

ber 51.3 Hence,;the outer edges of diaphragm legs 35a andz 35b in 5 arepulled respectively against the innersurfaces of side wall member plates42d and 41d so that'theorientation and location of ray defining edges35d and 350 of opening 40in each diaphragm 35: is determined byv theside walls41 and 42.

As analternate construction, control bar 61 may be of one piececonstruction with a periphery resembling thatknob 71tomove sidewallmembers 42 and 44in and out. Each drive unit gisjsubstantially identicalso only one will be described,namely, the onecontrolled by knob 71.,Knob 71 drives a shaft 71a in Fig- 3 having a pinion 72 thereon in Fig.10 rotatably carried in side,

wall member 41. Pinion 72 meshes with and drives,

gear 73 which in turn drives gear 74, carrying reSPQctivelypinions "73aand 74a,' all'rotatably mounted in side wall member 41'. In Fig. '11,the corner'member plates 51a and 54a have sector gears 75and 76 respec-itively secured thereto and adapted to be driven by pinions 7% and 73arespectively. Back-up rollers 77 and 78 keep the racks engaged againsttheir respective pinions with these rollers rotatably carried by s'idewall member 41 In the opposite side wall member 43 in Fig. 3 are locatedsimilar gears, pinions, sector gears andback-up rollers with the drivebetween them being provided through gears73', 79,30 and81 in Fig. '11;gear 81, universal joint 82, cross shaft 83, universaljoint 84 and gear85 in Fig. 6; and gears 85, 86 and 87in Fig.3.

A similar gearing and drive construction is provided between controlknob 70 'and side wall members '41 Hence, one pair of opposite side Wallmembers, such as 42 and 44, may be swung in or out by knob 71independently'of the'other sidewall members 41 and '43 to contractorrexpand the ray bea'm forming opening 40 in'only one dimension,such asdimension A inFig; 5L"

The other dim'ension' B is controlled by knob 70; Rota tioh of gears 73and 74 in Fig; 1 1 will drive corner member plates 51a and '54b'eitherinto or out of'their' respective sidewall'rnember 41. By properlycorrelating and phasing movements of control knobs 70 and 71,- thehousing may be changed in shape from a square prism in Fig. 3 toeither'a square or rectangular'pyramid so as to obtain all the differentbeam'shapes shown in.

Figs. 13 and 14; It should be noted that after a pair of these oppositeside walls are properly assembled equidistant from the longitudinalcentral axis of the beam, the teeth of gears 73, 73a, 74, 74a, 75 and 76will maintain this equidistant relationship.

The weight of all of these diaphragms 35, 36, 37 and 38 is slidablysupported by an expandable frame when-the ray beam is directeddownwardly from the source 20 in the manner shown in the drawings. Theframe is probably best shown in Figs. 3, 5, 7 and -8. Four bottom framecorners 91, 92, 93 and 94 are provided with four pairs of bottom frameguide rods 95 and 96 telescopical-. ly connected in aligned holes inadjacent corners to-permit the expansion thereof. Between each pair ofadjacent corners, a hinge construction is provided. These four hingeshave respectively upper leaves 101, 102, 103 and 104 pivotally connectedby hinge pins, 105.. to lower leaves.97, 98, 99 and 100.v The upperleaves serve as the spacer between'the inner and outer plates of therespective side wall members 41, 42 43 and 44, while the lower. leavesare bottom frame supports with .each rigidlyrse-i cured to one pair ofguide rods 95 and 96. Therefore as the side wall members and cornermembers move outwardly from the Fig. 3 to the Fig. 8 position, thebottom frame corners 91 to 94 move from the Fig. 4 position in contactwith the bottom frame supports 97 to 100 outwardly to the Fig. 7position by telescoping over their associated guide rods 95 and 96. Theexpandable frame is rigidly carried by the side wall members and iscentrally located with respect thereto by means of bottom frame supports97-100 and their respective guide rods 95 and 96. The bottom framecorners 91-94 provide support for the lower ends of the control bars61-64 and for the diaphragms 35-38.

A bottom cover for the collimator is provided by four cover plates 111,112, 113 and 114 of identical construction, as shown in Figs. 1 and 2.For example, plate 111 has a bottom wall 111a and a turned-up sideflange 111b, as shown in Fig. 1. These plates 111, 112, 113 and 114 aresecured respectively by screws to bottom frame supports 97, 98, 99 and100 in Fig. 7 so that the space between them always corresponds with theproper opening 40 for the ray beam because these cover plates will movein and out with the expandable frame.

It has been found that a suitable design is obtained with the presentconstruction with the following dimensions. The treatment distance fromsource 20 to the skin is about 40 centimeters while the lower end of thecollimator, designated by cover plates 111114, is approximately 25centimeters from the source 20. The range of field sizes formed byopening 40 is from 4 x 4 cm. square to 15 x 15 cm. square. Also, anyrectangle having either dimension between 4 and 15 cm. is obtainable. Ofcourse, collimators of this design for other field sizes and treatmentdistances could be easily produced. Any field size, (square,rectangular, or any other suitable shape) may be obtained. The stack ofdiaphragms 35-38 is formed in thirteen layers with each being one-halfinch thick and each diaphragm having overall dimensions of 4% by 2inches. The stack is 6% inches high. When the collimator diaphragms arein the Fig. 3 and Fig. 5 position, prismatic beam C in Fig. 13 isproduced. When they are expanded into the Fig. 7 and 8 position, a beamof square pyramid form D in Fig. 13 is produced with the slope of thepyramid sides equal to the slope of the side wall members 41-44 of thehousing. In this pyramid form, the sides and edges of the pyramid (theedges being shown by lines D1 and D2 in Fig. 8) run through the lateraledges of the source 20 in the manner shown in Fig. 8. This is especiallytrue when an other-than-point source 20 is used. It should be noted thatthe sides of the prism in Fig. 3 also extend through the lateral edgesof the source in a similar manner. This is also true of the intermediateadjusted positions of the collimator.

This construction provides good shielding from stray rays emanating fromsource 20 and also provides a collimator of compact overall length alongthe axis of the beam. It should be noted that at least some portions ofthe diaphragms in each set overlap in every adjusted position, includingthe maximum spread apart position in Fig. 7. These diaphragms not onlyoverlap along the axial length of the beam but also are in contact withthe axially adjacent diaphragms to provide a dense relationship toreduce leakage. The inner edges of the diaphragms form opening 40 with aclosed perimeter for forming the rays emanating from the source into aray beam. The overall height, or length along the axis of the beam, ofthe stack of diaphragms 35-38 remains constant during adjustment betweenthe Fig. 3 and 8 positions because the diaphragms slide one upon theother and the expandable frame supporting them at the bottom ispivotally connected by hinge pins 105 to the side wall members.

The diaphragm sets are slidably mounted and supported by the adjustableframe. Each set is slidably supported by its adjacent sets with the setsarranged in layers along the length of the beam. Each diaphragm hasstainless steel facing plates, such as plates 35 on top and bottom sothat sliding of the layers takes place at the junction of the steelsurfaces with minimum friction and minimum wear while the lead platecenter section, such as 35e, provides maximum ray absorption. Framecorners 91-94 have suflicient contact with the terminal edges of thediaphragms to support their weight even in the expanded position of Fig.8.

When the diaphragms are in the fully expanded position of Fig. 7 or Fig.8, it is desirable to provide spacers located axially between thediaphragms along the length of the beam to support correspondinglypositioned diaphragms in different layers. As the diaphragms moveoutwardly, voids are created in other places than in the central opening40; note Fig. 7. Two difierent type spacers are provided to give propersupport.

First, sleeves 66 around the control bars 61, 62, 63 and 64 serve notonly as spring holder sleeves but also as spacer sleeves since the axialdimension of each is equal to the thickness of the transversely aligneddiaphragm adjacent thereto. These spacer sleeves 66 are provided in twoopposite corners of each layer and in all four corners in each diaphragmset. Each spacer remains in the same relative position to its associatedcorner of the housing for the different collimator adjustment sizesbetween the Fig. 3 and Fig. 8 positions. They thus maintain the properspacing between the diaphragm in the expanded position of Fig. 8 that isprovided by the diaphragms themselves in the fully closed position shownin Figs. 3 and 5. Each L-shaped diaphragm has a notch, such as notch 35in diaphragm 35, cut out of the outer surface of its longer leg toprovide clearance for the associated spacer when the collimator is fullyclosed.

Second, the short leg of each L-shaped diaphragm helps support andmaintain the spacing between the long legs of the adjacent diaphragms.Note how short leg 35a in Fig. 7 helps support long 38b of diaphragm 38in the fully expanded position of Fig. 7. Also, the inner edge of thisshort leg forms a portion of the wall of the opening 40 in all positionsof adjustment and is always less than or equal to the dimension of theopening 40 parallel thereto. Compare dimension B in Fig. 5 with thehorizontal dimension of the largest square opening 40 in Fig. 7.

The edges of the beam are sharply defined in all positions ofadjustment. This is true because all portions of the inner edges of eachL-shaped diaphragm forming the ray beam lie in a plane perpendicular tothe axis of the beam in every position of adjustment. Hence, the edgesof the beam will be sharply defined on a fiat target arrangedperpendicular to the beam axis. If some of the portions of a beamdefining straight edge were in different planes, the beam edge formedthereby would be a fuzzy instead of sharp.

L-shaped diaphragms normally do not lend themselves to form bothrectangular and square beams because of adjustment problems. However, inthe present construction, one dimension of rectangular beam opening 40may be changed while another dimension remains constant. Also, theillustrated construction permits adjusting each diaphragm in twoditferent perpendicular directions both lying in .a common planetransverse to the beam axis.

Two different types of corner member constructions are illustrated inFigs. 9 and 9a. The basic difference between the two is in theconnecting portion 51c or 151a. Connecting portion 510 forms a hingealong the vertex of the corner or along the edge of the pyramid formedby the housing. Hinge plate 51a has a generally cylindrical socket end51:11 wrapped around a cylindrical pivot pin end 51111 formed on hingeplate 51b. Hence, this construction permits relative movement of thewalls 51a and 51b not only pivotally about the longitudinal hinge axisof end 51b1 but also along the longitudinal hinge axis, if such lastmentioned movement is required during the change in shape of thehousing. An inwardly aoaaeso directed lug 51:12 :istormed onthe.periphery ofiithe socket lporti'omextending lalon'gthe. length iof.-.the, .hingelini responding respectively to-plates 51a and' 51b in FigJ9a The slot 151d has made the folding operation easier and moreaccurately performed. The slot, having also had its-side wallsfoldedinwardly, forms a dovetail slot or groove running along the length ofand inside the vertex of the corner member. A slide memb er, taking theform of the head of a rivet 152 in the presentdisclo'sure, is slidablyretained in the groove lSld fortravelalong the length of the grooveifnecessary. The opposite ends of each spring 67 are adapted to bedetachablysecured to one of the rivets 152 so that the spring 67 Wl l1pull its associated diaphragm into the vertex of the corner inember.This corner member 151is of rigidangularformw tion so that itsconstruction is much simp'ler thanthe corner member shown in Fig. 9.'With the Fig. 9a construction, the centers of curvature of the sectorgears 75 and 76 in Fig. 11, and those in the other three housing wallmembers, preferably coincide with .thehing'e axes of pivot pins 41a44aso that relative movement between the hinge plates 151a and 1 51b is notnecessary during adjustment of the housing between theFig. 3 and Fig. 8positions.

However, the hinge construction in ,Fig. 9 does not necessarily needthiscoincidence of the pier axes. and the centers of curvature of the sectorgear si since relatiye movement is possible between the hinge plates intwo different directions. i i i i Alternate constructions within thescope of the present invention readily suggest themselves. First, inFig. 5, inner plate 51a is carried by cQrner member 5 1 ;whilestraddling plates 41c and 41d are carried byv side Wall member 41.However, cornermember 51 may be formed. with the straddling plates whileside wall. member 41 has the singleintermediate plate, ifso desired,"Second, in Fig. 5, correspondingly positioned diaphragms 3 are connectedto corner member 51, 38 to 52, 36;;to 53 and 37 to 54. However,correspondingly positioneddiaphragms may be connected with one'of .theirassociated side walls instead of a corner member. This is especiallytrue if the diaphragms have a straight single beam defining edge insteadof being L -shaped.

Indicators are provided for registeringthe size of the opening40-independently of the gear type driving or operating mechanisms shownin Fig. 11. Here, two identical indicator constructions are provided,one for the housing side wall members controlled by knob 71 and theother for those controlledby knob 70. Since these indicatorconstructions are identical, only, one is shown in detail and will bedescribed in detail. Adjacentknob 71 in Fig. is the.indicator,120. for.registering movement of side wall members 41 and 43 by. control knob.70. Indicator 120 has an indicia bearing disk.121 ,.in Figs. 3 and 10with a series of numbers thereonand isadapted to rotate about a centralshaft carried by side Wall: member 41, which is carried with the raybeamdefining inner.

edges 35d of correspondingly positioneddiaphnagms 35;Therindiciaisadapted to alignwith a scale: on, the edge of anfopening 122 inside wall member 41,upon rotation of.

the disk'121. A cable 123 in Fig. 3 is wrappedaround a drum. 121acoaxiallyv carriedby the disk 121 inFig. 3 ,v

extendsv downwardly ab ont anidler pulley 124i rotatably mounted on apivot pm 105 in Figs. 7, extends across the center of the ray beamopening 40, is anchored eliminated from the cable. carried by. theopposite side wall'rriember 43, its position will be a function of theinner raybeam, defining edge of diaphragm 36. Therefore, the readingonindicator 121 in window 122 will beat functionof the dimension B in Fig.5 of ray beam opening 40." In similar manner, the

dimension A'lin Fig. 5 willbe shown by its indicator operativelyconnected to the cable 123 in a similar man-v ner in Fig. 7. Theseindicators will register the size of the opening 40. independently ofthe gear drives in Fig.'

11 so as to eliminate. any back lash error that may occur duringmovement of the'housing between the different adjusted positions. 7

These crossed cables in Fig. 7 serve another function. The cables 123and 123- always cross'the center of the path of the beam through theopening 40- at the end of the collimator most remote from the source 20(at the bottom in Fig. 3) because each cable" is positioned centrallywith respect to the opposite side wall members 41 and 43 or 42-and 44 byits associated-pulley 124 and nut 125. In Fig. 3, a light source isprovided in the base 32 adjacent the ray source 20 for providing withthe helpof mirror 131, extending across base opening 32d, a downwardlyextending light beam through the opening 40 coincidingwith the highenergy ray beam. If the light source 130 throws downwardly a light beamduring use of'the high energy ray beam, the shadow cast upon the targetby the crossed cables 123 and 123" will indicate the center of the raybeam to aid in its usage. The cross idifiired will be sharply definedsince the cables are fairly near the target and remote from' the lightsource 130.

Variouschanges in details and arrangement of parts can be made by oneskilled in the art without departing from either the spirit of thisinvention or the scope of the appended claims.

What is claimedis:

1'. A collimator for high energy rays emanating from a source,comprising a plurality of spaced diaphragm sets, each set being composedof a plurality of ray absorbing mow/able diaphragms defining an openingwith a closed perimeter for forming said rays into a beam, and operatingmechanisms with each mechanism operatively connected withcorrespondingly positioned diaphragms in each set for adjusting all ofsaid correspondingly and aplurality of housing side wall me'rnberspivotally connected to said'base', and including means operativelyconnecting respectively one side wall member to each group ofcorrespondingly positioned diaphragms.

2. A collimatdr 'for high energy rays emanating from a source,comprising a plurality of spaced diaphragm sets, each set being composedof a plurality of ray absorbing' movable diaphragms defining an openingwith a closed perimeter for forming said rays into a beam, and operatingmechanisms with each mechanism operatively connected withcorrespondingly positioneddiaphragms in each set for adjusting all orsaid correspondingly positioned diaphragms simultaneously; saidmechanisms including an 'even number of housing sidewall members,including means 'operatively connecting one side Wall member toeachgroup of correspondingly positioned diaphragms, and including means forswinging opposite side wall members in orout independently of the otherside wallmembers to contractor expand saidopening in only one dimension.

3-. A- collimator for high energy rays emanating from a m comprising:.pl rality fi p d di p a m;

ing movable diaphragms defining an opening with a closed perimeter forforming said rays into a beam, and operating mechanisms with eachmechanism operatively connected with correspondingly positioneddiaphragms in each set for adjusting all of said correspondinglypositioned diaphragms simultaneously; said mechanisms including aplurality of housing side wall members operatively connected togetherfor relative pivotal movement, and including resilient means operativelyconnecting respectively one side wall member to each group ofcorrespondingly positioned diaphragms to make them follow theirassociated side wall member.

4. A collimator for high energy rays emanating from a source, comprisinga plurality of spaced diaphragm sets, each set being composed of aplurality of ray absorbing movable diaphragms defining an opening with aclosed perimeter for forming said rays into a beam, and operatingmechanisms with each mechanism operatively connected withcorrespondingly positioned diaphragms in each set for adjusting all ofsaid correspondingly positioned diaphragms simultaneously; saidoperating mechanisms including a plurality of side wall members,including a plurality of corner members each operatively connectingadjacent side wall members to form a housing therewith around said sets,and including means operatively connecting at least one corner member toa group of correspondingly positioned diaphragms.

5. A collimator for high energy rays emanating from a source, comprisinga plurality of spaced diaphragm sets, each set being composed of aplurality of ray absorbing movable diaphragms defining an opening with aclosed perimeter for forming said rays into a beam, and operatingmechanisms with each mechanism operatively connected withcorrespondingly positioned diaphragms in each set for adjusting all ofsaid correspondingly positioned diaphragms simultaneously; saidoperating mechanisms including a plurality of side wall members,including a plurality of corner members each operatively connectingadjacent side wall members to form a housing therewith around said sets,and including drive means operatively connecting each side wall memberto at least one of its adjacent corner members for causing relativemovement therebetween.

6. The combination of claim wherein said drive means includes meshingpinion and sector gears connected respectively to adjacent members.

7. A collimator for high energy rays emanating from a source, comprisinga plurality of spaced diaphragm sets, each set being composed of aplurality of ray absorbing movable diaphragms defining an opening with aclosed perimeter for forming said rays into a beam, and operatingmechanisms With each mechanism operatively connected withcorrespondingly positioned diaphragms in each set for adjusting all ofsaid correspondingly positioned diaphragms simultaneously; saidoperating mechanisms including a plurality of side wall members,including a plurality of corner members each operatively connectingadjacent side wall members to form a housing therewith around said sets,including a control bar extending through aligned holes in a group ofcorrespondingly positioned diaphragms, and including means forresiliently pulling said bar toward one of said corner members and saidlast mentioned diaphragms against side wall members adjacent said lastmentioned corner member.

8. A collimator for high energy rays emanating from a source, comprisinga plurality of spaced diaphragm sets, each set being composed of aplurality of ray absorbing movable diaphragms defining an opening with aclosed perimeter for forming said rays into a beam, and operatingmechanisms With each mechanism operatively connected withcorrespondingly positioned diaphragms in each set for adjusting all ofsaid correspondingly positioned diaphragms simultaneously; saidoperating mechanisms including a plurality of sidewall members,

including a plurality of corner members each operatively connectingadjacent side wall members to form a housing therewith around said sets,and at least one of said corner members is an angle member with theplanar walls thereof operatively connected to move respectively in theplanes of the adjacent side wall members.

9. The combination of claim 8, wherein said last mentioned corner memberis of rigid angular formation.

10. The combination of claim 8, wherein said side wall members are fourin number with each pivotally mounted along an axis and said axes definea rectangle around said beam in a plane normal to said beam, all of saidcorner members are of rigid angular formation and each is pivotallymounted to swing about either of two of said axes.

11. The combination of claim 8, wherein said last mentioned cornermember is hinged along its vertex.

12. The combination of claim 11, wherein said hinge is constructed topermit relative movement of said planar walls along the hinge axis.

13. The combination of claim 8, wherein means operatively connectscorrespondingly positioned diaphragms in each set to the vertex of saidlast mentioned corner member.

14. The combination of claim 13, wherein said last mentioned cornermember is of rigid angular formation and has a groove running along thelength of and inside the vertex thereof, and said connecting meansincludes a slide member slidably retained by said groove for travelalong said groove and a flexible connector operatively connecting saidslide member and at least some of said correspondingly positioneddiaphragms.

15. The combination of claim 8, wherein said operative connectionbetween the wall of one corner member and one side wall member includesone member having a plate telescoped between two plates spaced apart onthe other member.

16. A collimator for high energy rays emanating from a source,comprising a plurality of spaced diaphragm sets, each set being composedof four ray absorbing movable diaphragms defining a rectangular openingfor forming said rays into a ray beam, operating mechanisms with eachmechanism operatively connected with correspondingly positioneddiaphragms in each set forming one of four diaphragm groups foradjusting all of said correspondingly positioned diaphragms in one groupsimultaneously, two indicators connected respectively one to each ofadjacent correspondingly positioned diaphragm groups, two cables withone for each indicator, each cable having one end carried by a diaphragmin the group positioned opposite the indicator and the other endoperatively connected to said indicator for actuation thereof responsiveto the size of said opening, said indicators and cables being arrangedso that said cables cross the center of said ray beam at the end of saidsets remote from said ray source, a light source adjacent said sourceproviding a light beam through said opening corresponding with the highenergy ray beam, and means for adjusting at least some of saiddiaphragms to change the size of said opening while automaticallymaintaining in each adjustment said cables crossing the center of thepath of said beam and opening, whereby the shadow cast by said cablesindicates the center of said beams.

17, A collimator for high energy rays emanating from a source,comprising a plurality of L-shaped ray absorbing movable diaphragmsdefining a closed rectangular opening for forming said rays into a beam,andmeans operatively connected with said diaphragms on opposite sides ofsaid rectangular opening for relatively moving some of them inrectilinear motion parallel to one side of said rectangular opening, andfor moving others of said diaphragms in rectilinear motion in thedirection at right angles to said first motion, whereby to change eachdimension of said rectangular opening independently of its otherdimension.

18. A collimator for forming into a beam high energy rays emanating froma source, comprising a plurality of spaced diaphragm sets of two pairseach, said pairs in adjacent layers, said diaphragms all having L-shapedbeam defining edges with the vertexes of the edges of .one pair lying attwo opposite corners of a rectangle and with the vertexes of the edgesof the adjacent pair lying at the other two opposite corners of saidrectangle, said diaphragms having legs in adjacent pairs lying along thesame side of said rectangle and extending in opposite directions alongsaid side and overlapping each other, and means operatively connectedwith said diaphragms on opposite sides of said rectangular opening forrelatively moving them in rectilinear motion in the direction of oneside of said rectangular opening and for moving others of saiddiaphragms in rectilinear motion in the direction at right angles tosaid first motion, whereby to change each dimension of said rectangularopening independently of its other dimension.

19. A collimator as in claim 18 wherein the dia phragms in all of saidlayers are flat and slidingly engage the diaphragms in adjacent layersto provide a dense beam-shielding relationship.

20. A collimator as defined in claim 17 including two indicators, cablescarried respectively one by one of said diaphragms which is movable inthe direction of one side 14 of said rectangle and the other by one ofsaid diaphragms which is movable at right angles to said first motion,and each of said cables operatively connected to one of said indicatorsto actuate the latter responsive to the dimension of said opening in thedirection of the associated rectilinear motion, said cables intersectingat the center of said rays passing through said collimator at the endthereof remote from said source, and a light source adjacent said raysource providing a light beam through said opening coinciding with theaxial center of said rays, whereby the shadow cast by said cablesindicates the center of said collimated rays.

References Cited in the file of this patent UNITED STATES PATENTS1,909,118 Raab May 16, 1933 1,976,179 Mannl Oct. 9, 1934 2,181,620 HauptNov. 28, 1939 2,187,246 Nerwin Jan. 16, 1940 2,542,196 Haupt Feb. 20,1951 2,544,779 Daly Mar. 13, 1951 2,614,224 Wright Oct. 14, 19522,675,486 Green et a1. Apr. 13, 1954 2,844,736 Johns et al. July 22,1958 2,881,329 Peyser Apr. 7, 1959

